It may be helpful to understand what is meant, first, by the terms "cement" and "concrete," and, consequently, what is meant by the phrases "cement additive" and "concrete admixture." The term"cement" is used generally to refer to Portland cement, which is a hydraulic cement, produced by pulverizing clinker consisting essentially of hydraulic calcium silicates, usually containing one or more forms of calcium sulfate as an interground addition. The term"hydraulic cement" refers to one that hardens by a chemical interaction with water. A "cement mortar" is a mixture of cement fine aggregate (e.g., sand), and water. However, the term"concrete" is used herein to refer to a mixture prepared from a cement (acting as a hydraulic binder), fine aggregate (e.g., sand), course aggregate (e.g., gravel), and water which is added to initiate the hardening of the cement binder.
A "cement additive" is a material used to facilitate the manufacturing of the cement or to improve its quality. Cement additives have several uses, for example, such as (1) grinding aids to enhance the efficiency of the mineral grinding process (including clinker) and to improve the flowability of the ground material, or to prevent phenomena known as "pack set" or "silo set"; (2) quality improvers to change the set time of the cement; (3) workability improvers to reduce the water demand of the cement and/or to increase its workability; (4) masonry/mortar additives to improve the workability cements intended for use in masonry applications (as well as to entrain air, increase water retention or board life, control set time, provide water resistance or increase strengths); and (5) slurry thinners to reduce the water content in raw material slurries.
A "concrete admixture" is a material other than hydraulic cement, water, and aggregates used as an ingredient of concrete or mortar and added to the concrete batch before, during, or after mixing and before hardening. Admixtures are used for modifying one or more properties of the concrete in such a way as to make it more suitable for a particular purpose or more economical.
Some of the major reasons for using admixtures are: (1) to achieve certain structural improvements in the resulting cured concrete; (2) to improve the quality of concrete through the successive stages of mixing, transporting, placing, and curing during adverse weather or traffic conditions; (3) to overcome certain emergencies during concreting operations; and (4) to reduce the cost of concrete construction. In some instances, the desired result can only be achieved by the use of an admixture. In addition, using an admixture allows the use of less expensive construction methods or designs and thereby offsets the costs of the admixture.
The term "concrete admixture" as used herein and after shall also mean and include admixtures for masonry concrete as well. A masonry concrete mix is one having a low moisture content. Some of the reasons for using a masonry admixture are: (1) to reduce the passage of water through the finished unit; (2) to improve the appearance of the end product; (3) to lower production costs; (4) to reduce production losses due to breakage; and (5) to reduce wear on the production machinery.
Typically, cement additives and concrete admixtures are sold as a "finished product" shipped in a tanker truck having a number of compartments containing other finished products, or they are shipped in dorms, in "totes" (e.g., 300 gallon plastic barrels), or in other bulk forms. The term "finished product" means that the additive or admixture is comprised of a blend of "raw material" components. Raw admixture materials, for example, may include lignosulfonate, corn syrup, an amine, etc. which is either mixed with water and/or another raw material.